Hi and welcome to Server Fault. Please do not cross post on the variosus Stack Exchange websites. This is discouraged and against the rules outlined in the FAQ. Cross post URL: superuser.com/questions/594536/…
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slmMay 12 '13 at 6:06

Do you have opensm running? It may not be required if your switch does manangement. Orange link lights normally indicate an active connection. Next step would be to try ibping -S on one host and run ibping [other hostname] on the other machine to verify your network is working. In regards to OpenMPI, it will try to run with the fastest interconnect available. You can specify interconnect on the command line. open-mpi.org/faq/?category=tuning#selecting-components
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chuckNov 26 '13 at 14:48